This invention relates to an apparatus for separating logs from a pile so that the logs may be taken individually for further processing.
Logs received at a typical wood processing facility, such as a sawmill, vary both in diameter and length. The logs may be tapered differently from one another and come in a variety of physical shapes, all of which are different from the ideal log shape, which is straight, has a perfectly circular cross-sectional area and a constant diameter throughout its length. Finally, the logs are typically deep piled on an in-feed log deck, such that the logs become skewed, crossed and/or tangled. It is generally necessary to feed the logs to the processing facility one log at a time. It is also desirable that there be no interruption in the flow of logs into the wood processing facility. A device is needed to accomplish the task of separating logs received as outlined above.
Such a device is often called a log singulator. A log singulator separates logs from a pile and feeds them one at a time to a log processing facility, typically by way of an out-feed conveyor. Log singulators come in different types.
xe2x80x9cStep sorterxe2x80x9d singulators, such as the devices shown by U.S. Pat. No. 5,423,417 (xe2x80x9cLog Ladderxe2x80x9d), U.S. Pat. No. 5,257,688 (xe2x80x9cStep Feederxe2x80x9d) and U.S. Pat. No. 5,174,351 (additions to xe2x80x9cStep Feederxe2x80x9d), sort logs in a series of steps which are distributed horizontally along a small vertical incline. The main disadvantages of such singulators are imprecise separation of logs (i.e. tendency to carry more than one log at a time toward the wood processing facility) and high floor area occupied within the processing facility. Another common disadvantage of some of these singulators is the absence of surge and catch-up features. Such features are usually used to ensure that logs are fed at an optimal rate to a wood processing facility.
xe2x80x9cRotary sorterxe2x80x9d singulators, such as the device described in U.S. Pat. No. 5,011,024 (xe2x80x9cRotary Log Sorterxe2x80x9d), have drums with pockets or arms that rotate continuously. The pockets or arms carry logs one at a time to an out-feed conveyor. A main problem with such singulators is that occasionally more than one log will be taken in by the pockets or arms. Such singulators are also poor at efficiently raising logs vertically, as they occupy more floor space than desired when doing so. Another problem associated with such singulators is the inability to singulate oddly-shaped logs. Another common disadvantage of such singulators is the absence of surge and catch-up features to ensure that logs are fed at an optimal rate to a wood processing facility.
xe2x80x9cOscillating quadrant/arcxe2x80x9d singulators, such as the device described in U.S. Pat. No. 5,119,930 (xe2x80x9cQuadrant Log Feederxe2x80x9d), elevate logs along a curved surface. The main disadvantages of such singulators are imprecise separation of logs and low singulation speed (i.e. the number of logs per minute that can be separated from an in-feed log deck and fed, one at a time to an out-feed conveyor). Also, such singulators do not provide for optimal surge and catch-up features to ensure that logs are fed, one at a time and at an optimal rate, to an out-feed conveyor.
There is therefore a need for log singulators which address at least some of these deficiencies. There is a particular need for singulators which can singulate logs with increased precision. There is a further need for high speed log singulators which occupy minimal floor space area and substantially elevate logs vertically to take advantage of the vertical space available within a typical wood processing facility. There is a further need for singulators which can handle logs with a large range of diameters and a large range of shapes. There is further a need for singulators with surge and catch-up features which can help to feed logs at an optimal rate to a wood processing facility.
This invention provides log singulators which allow for the vertical singulation of piles of logs fed from typical in-feed log decks, so that these logs may be fed individually to a wood processing facility.
This invention provides log singulators comprising arcuately oscillating primary lifting devices, adapted for elevating logs from a log input mechanism to an unloading station, wherein the logs are raised by vertically successive primary lifting devices. Vertically adjacent primary lifting devices may move synchronously in opposite directions to one another.
This invention further provides log singulators comprising guiding barriers, against which the primary lifting devices raise the logs. In a preferred embodiment of this invention, the guiding barriers comprise sets of guiding rails, adjacently separated by recessed plates.
Preferably, the primary lifting devices comprise pivotally mounted lifting surfaces extending through the guiding barriers against which the lifting surfaces are raising the log. The lifting surfaces are preferably located at end of fins extending through the guiding barriers. The point of pivot is recessed away from the log input mechanism and the lifting surfaces slope toward the guiding barriers.
In the preferred embodiment of this invention, each set of guiding rails comprises adjacent guiding rails spaced apart a sufficient width to permit the passage of the fins and of the lifting surfaces.
According to this invention, the guiding barrier is shaped so that only one, of either the largest log or the smallest log which the singulator is expected to handle, can be carried upward at a time by the lifting surfaces.
The guiding barrier is divided in two sections: an upper section and a lower section. The separation point between the upper and the lower section is located around the point of contact a largest log (which the singulator is expected to handle) has with the barrier, when:
a) the largest log is positioned on the lifting surfaces and resting against the guiding barrier, and
b) the lifting surfaces are located at their lowest position.
The shape of the lower section is such that, when the lifting surfaces are located at their lowest position:
a) a smallest log (which the singulator is expected to handle) positioned:
i) on the lifting surfaces, and
ii) resting adjacently and outwardly from the guiding barrier against any log (falling within a range of logs which the singulator is expected to handle) which is positioned on the lifting surfaces and resting against the guiding barrier,
xe2x80x83would have its centre of gravity located outside of the tipping point of the lifting surfaces; and
b) a largest log (which the singulator is expected to handle), positioned:
i) on the lifting surfaces, and
ii) resting against the guiding barrier,
xe2x80x83would have its centre of gravity located inside of the tipping point of the lifting surfaces.
The shape of the upper section is such that, throughout the movement of the lifting surfaces raising the largest log, the centre of gravity of the largest log remains inside the tipping point of the lifting surfaces.
The vertically highest (i.e. upper) primary lifting device carries logs to the unloading station. Pursuant to the invention, the unloading station can comprise oscillating secondary lifting devices, adapted for moving logs to an out-feed device, wherein the logs are moved by horizontally adjacent secondary lifting devices. Horizontally adjacent secondary lifting devices may move synchronously in opposite directions to one another.
According to this invention, the unloading station may comprise secondary holding notches, wherein logs are moved, in a stepwise manner, over horizontally adjacent secondary holding notches, to the out-feed device.
The face of the secondary holding notches, against which logs are raised, preferably slopes away from the path of movement of the relevant secondary lifting device.
Preferably, each secondary lifting device comprises secondary lifting surfaces extending through the secondary holding notches against which the secondary lifting surfaces are raising logs. The secondary lifting surfaces preferably slope toward the relevant secondary holding notch.
The unloading station may comprise a sensor, adapted to stop the movement of the primary lifting devices when the sensor has detected that the first secondary holding notch is unavailable to receive a log. The unloading station may also comprise a sensor, adapted to stop the movement of the secondary lifting devices when the sensor has detected that the out-feed device is unavailable to receive a log.
The unloading station may also comprise a surge area, adapted for receiving a log from the upper primary lifting device when the first secondary holding notch is unavailable to receive a log. In this embodiment, the unloading station may comprise a sensor, adapted to stop the movement of the primary lifting devices when the sensor has detected that the surge area is unavailable to receive a log.
This invention further provides a method for vertically singulating a pile of logs fed transversely from an in-feed log deck, the method comprising of elevating one of the logs along vertically successive arcuate paths up to an unloading station. The step of elevating one of the logs can be accomplished by providing vertically successive arcuately oscillating lifting devices. The step of elevating one of the logs can further be accomplished by providing vertically successive barriers against which the one log is raised by the lifting devices.
The step of providing vertically successive barriers comprises providing barriers whose shape are as outlined above.
Further features and advantages of the invention are described as follows.